hey does anyone know the limitations of a government hair follicle test?

Question

I know the standard hair follicle test is limited to a year of detecting drug use. My girlfriend claims the test used by the federal government is able to detect drug usage from years back. Im not sure. The whole Britney Spears shaving the head thing spurred this conversation. Can anyone help? Thanks.

Answer 1

A clever dentist(?) determined that Napoleon had been poisoned with arsenic while exiled on the Isle of Elba. They had an authentic hair sample that had been taken from his head at death and preserved. When the hair was bombarded (with neutrons?) the hair irradiated in such a way that the constituents of the hair could be evaluated. The hair increased in strength for arsenic monthly, about the time that a bottle of his favorite wine arrived from the mainland. Examining the hair along its length provided a time line. If the hair is ground up only an average exposure to ingested chemicals during the growth period for the length of hair could be determined.